Information recording/reproducing apparatus

ABSTRACT

A playback error associated with overwriting on a narrow-width track is prevented from occurring in the overwritten portion. A signal generator ( 11 ) generates a signal of a predetermined data pattern that stabilizes the operation of a synchronizing pulse generator of a playback system (shown in a separate figure). A timing generator ( 4 ) switches over a switch ( 12 ) to the output of the signal generator ( 11 ), at least a period of time equivalent to writing of one track before the main signal is input. When a signal of the predetermined data pattern from the signal generator ( 11 ) has been output, the timing generator ( 4 ) switches over the switch ( 12 ) to the main signal. The playback system includes a circuit which discriminates between the predetermined data pattern and the main signal data from a playback signal generated by playing back a record on a magnetic tape (T).

This application is a 371 of PCT/JP02/05231 May 29, 2002.

TECHNICAL FIELD

The present invention relates to information recording and playbackapparatuses and specifically to an information recording and playbackapparatus for preventing a playback error in an overwritten portionassociated with an increase in recording density achieved by narrowingthe track width of a magnetic tape apparatus.

BACKGROUND ART

A typical apparatus for reading and writing information throughsequential access, such as a magnetic tape recording and playbackapparatus, reads and writes information for every track and thereforerequires highly precise tracking (track following function) duringrecording and playback of information. In playback mode, the range ofthe track width corresponds to the scanning area of a playback head.

Such high-precision tracking is also required during overwriting(writing new information to an already-written tape), and a portionchanged by overwriting is also processed for every track.

A high density is achieved by narrowing the minimum writing unit (trackwidth); a narrowed track width, however, often prevents successfultracking.

In response to recent demands for recording media with increased storagecapacity, the effective track width is narrower than the width of thescanning area of the playback head, inevitably causing the width of thescanning area of the playback head to span two contiguous tracks in somecases.

Unfortunately, a conventional information recording and playbackapparatus often generates an error during playback due to a narrowedtrack width if the width of the scanning area of the playback head spanstwo contiguous tracks, especially if one of the two contiguous tracks isan already-written track and the other is a newly written track.

The mechanism of the generation of the error described above is asfollows: narrow-width tracks cause a track in a newly written portion toshift with respect to the original track or causes the frequency ofrecorded tracks to differ between the newly written portion and theoriginal portion due to differences in the recording system duringrecording, leading to poor frequency-locking of a phase locked loop(PLL) used in the playback system and finally to loss ofsynchronization. In short, such an error results from mixing of oldoriginal data and newly written data or a malfunction of the PLL.

In order to solve these shortcomings associated with the conventionalinformation recording and playback apparatus, an object of the presentinvention is to provide an information recording and playback apparatusfor preventing the generation of a playback error in a portion ofnarrow-width tracks having information overwritten thereon.

DISCLOSURE OF INVENTION

In order to solve the shortcomings described above, the presentinvention provides an information recording and playback apparatus usinga magnetic tape as a recoding medium, comprising signal addition meansfor adding a predetermined data pattern to the leading end of main datato be recorded onto the magnetic tape during recording, thepredetermined data pattern stabilizing the operation ofsynchronizing-pulse supply means of a playback system; data recordingmeans for recording data generated by the signal addition means onto themagnetic tape; and data discrimination means for discriminating, duringplayback, between the recorded predetermined data pattern and therecorded main data from a playback signal generated by playing back arecord on the magnetic tape.

The present invention is achieved by the recording system and theplayback system as described below. In overwriting (writing new data onold data) mode, the recording system allows the predetermined datapattern for one track (track-pattern data) to be additionally written atthe leading end of the newly written data, the predetermined datapattern stabilizing the operation of the synchronizing-pulse supplymeans (hereinafter referred to as PLL) used in the playback system. Inplayback mode of the newly written data, the playback system allows thePLL to receive a playback signal which includes a signal component ofthe predetermined data pattern. These features ensure that an accurateclock for playback synchronization is generated by the PLL of theplayback system from the beginning of playback of the newly writtendata, preventing the generation of an error during playback of the newlywritten data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a recording system of an informationrecording and playback apparatus according to an embodiment of thepresent invention.

FIG. 2 is a block diagram of a playback system of the informationrecording and playback apparatus according to the embodiment of thepresent invention.

FIG. 3 is an illustration in which a head of the playback system scansover the track information recorded on a magnetic tape by the recordingsystem of the information recording and playback apparatus according tothe embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will now be described withreference to the drawings.

FIG. 1 is a block diagram of a recording system of an informationrecording and playback apparatus according to the embodiment of thepresent invention.

The recording system of the information recording and playback apparatusaccording to the embodiment includes a signal adder 1 (signal additionmeans) which adds a predetermined data pattern to main signal data; arecording-signal processing circuit 2 (data recording means) whichconverts an internal signal (an additional signal component of thepredetermined data pattern and a signal component of the main signaldata) of data to be written into a recording signal; a recording head 3(data recording means) which records the data to be written based on theinput recording signal; and a timing generator 4 which determines thetiming for adding the predetermined data pattern to the main signaldata.

The signal adder 1 includes a signal generator 11 (signal generationmeans) which generates a signal of the predetermined data pattern and aswitch 12 (switching means) which toggles between the main signal (data)and the additional signal of the predetermined data pattern.

In FIG. 1, symbol T denotes a tape (magnetic tape) as a recordingmedium.

The recording-signal processing circuit 2 may, for example, be a D/Aconverter and others.

FIG. 2 is a block diagram of a playback system of the informationrecording and playback apparatus according to the embodiment of thepresent invention.

The playback system of the information recording and playback apparatusaccording to the embodiment includes a playback head 21 which convertsdata recorded on the tape T to a playback signal; a playback-signalprocessing circuit 22 which converts the playback signal to an internalsignal; an A/D converter 23 which performs A/D conversion of theinternal signal output by the playback-signal processing circuit 22; aPLL 24 which extracts a clock from the internal signal output by theplayback-signal processing circuit 22 and then supplies the A/Dconverter 23 with the extracted clock; and a signal discriminationcircuit 25 (data discrimination means) which discriminates between thesignal of the main signal data and the signal of the predetermined datapattern from the signal output by the A/D converter 23.

The operation of the information recording and playback apparatusaccording to the embodiment will now be described with reference toFIGS. 1 and 2.

First, the operation of the recording system will be described withreference to FIG. 1.

To record data on the tape T, the signal adder 1, which has received themain signal of the data, adds a signal of the predetermined data patternto the leading end of this main data and sends the resultant signal tothe recording-signal processing circuit 2.

More specifically, an external system for sending the data sends a datawriting notification to an input line (not shown in FIG. 1) of thetiming generator 4, at least a period of time equivalent to writing ofone track before sending the data.

Upon receiving the notification, the timing generator 4 switches overthe switch 12 of the signal adder 1 to the signal generator 11. As aresult, a signal of the predetermined data pattern generated by thesignal generator 11 of the signal adder 1 is sent to therecording-signal processing circuit 2. After the time equivalent towriting of one track has elapsed, the timing generator 4 operates theswitch 12 so that the recording-signal processing circuit 2 receives themain signal.

The signal of the predetermined data pattern generated by the signalgenerator 11 of the signal adder 1 may be of any kind that can bedetected with high sensitivity by the PLL 24 of the playback systemdescribed later and that can stabilize the operation of the PLL 24,which is capable of stably supplying an accurate clock when receivingthe signal. For example, the signal has a stripe pattern consisting oftwo different values repeated alternately and regularly (2T pattern).

The recording-signal processing circuit 2 converts the signal of thepredetermined data pattern generated by the signal generator 11 of thesignal adder 1 and the subsequent main signal to a signal for playbackand then sends the signal for playback to the recording head 3. Thisconversion may include D/A conversion and modulation.

The recording head 3 then records the signal for playback on the tape T.

The operation of the playback system (a counterpart of the recordingsystem described above) will be described with reference to FIG. 2.

First, the playback head 21 converts data recorded on the tape T to asignal for playback and then sends the signal for playback to theprocessing circuit 22.

The processing circuit 22 converts the sent signal for playback to theinternal signal and then sends the internal signal to the A/D converter23 and the PLL 24.

The A/D converter 23 performs A/D conversion of the sent internal signalusing the clock sent by the PLL 24 and then sends the resultant signalto the signal discrimination circuit 25.

The PLL 24 generates the clock (synchronizing clock) from the internalsignal sent by the processing circuit 22 and sends the clock to the A/Dconverter 23. This internal signal includes the signal component of thepredetermined data pattern recorded by the relevant recording system, inwhich the signal component of the predetermined data pattern is added tothe leading end of the signal component of the written data, therebyallowing the PLL 24 to ensure the generation of an accurate clock.

The signal discrimination circuit 25, which is characteristic to theplayback system of the present invention, discriminates between thepredetermined data pattern and the subsequent written data from theinternal digital signal sent by the A/D converter 23. The extractedpredetermined data pattern may be discarded.

FIG. 3 is an illustration in which the head of the playback system scansover the track information recorded on the magnetic tape by therecording system of the information recording and playback apparatusaccording to the embodiment of the present invention.

FIG. 3 is an illustration in which newly written tracks are generated byoverwriting on tracks which have been written before the recording bythe recording system.

A 2T-pattern-recorded track (T2) is provided with recorded data of thepredetermined pattern, which is a stripe pattern consisting of twodifferent values repeated alternately and regularly (2T pattern). Arecorded track (T1) is a track already recorded before overwriting andis contiguous to the 2T-pattern-recorded track (T2).

Playback-head scanning area SA (area scanned by the playback head 21)spans the recorded track (T1) and the 2T-pattern-recorded track (T2),often generating an error in a playback system of a conventionalinformation recording and playback apparatus. The present invention,however, prevents the generation of an error at this portion and thesubsequent portions by recording onto the 2T-pattern-recorded track (T2)a predetermined data pattern that can be easily detected by the PLL 24.

The embodiment of the present invention has been described in relationto the recording head 3 of the recording system, the recording head 3writing new data on the already-recorded tape T; in general, however,the recording head 3 of the information recording and playback apparatusaccording to the embodiment of the present invention allows data to berecorded onto the tape T having no information recorded thereon (virgintape) in the same manner as for overwriting.

As described above, additional data for one track is written at theleading end of data to be newly written during the overwriting processby the recording system, the additional data (predetermined datapattern) facilitating synchronization by the PLL used in the playbacksystem. Furthermore, a playback signal which includes a signal componentof the predetermined data pattern is input to the PLL during playback ofthe newly written data by the playback system, and thereby an accurateclock for playback synchronization is generated by the PLL of theplayback system from the beginning of playback of the newly writtendata. Thus, the present invention prevents the generation of an errorduring playback of the newly written data.

1. An information recording apparatus using a magnetic tape as arecording medium, the apparatus comprising: signal addition means foradding a predetermined data pattern for at least one track to theleading end of main data to be recorded onto the magnetic tape duringrecording; and data recording means for recording the data generated bythe signal addition means onto the magnetic tape.
 2. The informationrecording apparatus according to claim 1, wherein the predetermined datapattern is a stripe pattern consisting of two different values repeatedalternately and regularly.
 3. The information recording apparatusaccording to claim 2, wherein the stripe pattern is a 2T pattern.
 4. Theinformation recording apparatus according to claim 1, wherein the signaladdition means comprises: signal generation means for generating asignal of the predetermined data pattern; and switching means fortoggling between a signal of the data to be recorded onto the magnetictape and a signal of the predetermined data pattern.
 5. The informationrecording apparatus according to claim 1, wherein the magnetic tape is amagnetic tape any portion of which has written data or a magnetic tapeno portion of which has written data.
 6. An information playbackapparatus for playing back a magnetic tape having an additionalpredetermined data pattern for at least one track at the leading end ofrecorded main data, the apparatus comprising: data discrimination meansfor discriminating between the recorded main data and the recordedpredetermined data pattern from a playback signal generated by playingback a record on the magnetic tape.